| Heavy metal contamination has always been one of the key concerns of food safety.The commonly used detection methods for heavy metals in food in laboratories are liquid sampling detection methods based on mass spectrometry and atomic spectroscopy.These methods are usually complicated in pre-processing and operation procedures,and use a large amount of chemical reagents such as nitric acid and hydrogen peroxide,so they cannot be used for rapid detection of food.Based on the above problems,in order to meet the requirements of rapid detection of heavy metals in food,this experimental study established a rapid detection method for solid injection of multiple elements in food based on single wavelength excited energy dispersive X-ray fluorescence spectrometry.The results show that this detection method has the advantages of simple sample pretreatment,direct injection of solid tablet and non-destructive testing of samples,simple operation,sensitivity and precision to meet the needs of rapid food detection.The total detection time of various elements is 600 s,and the instrument is only 10 kg,which can provide an effective detection method for on-site and rapid screening of food.The main research contents and results of this paper are as follows:(1)Prepare the standard sample for rice composition analysis,and assign the value to the standard sample.In this paper,five concentrations of rice composition analysis standard samples(As,Pb,Cd)were prepared,and the uniformity and stability of the standard samples were verified,and the joint calibration of three laboratories and the calculation of the uncertainty of the standard products were carried out.(2)Standard curve quantitative method was used to establish the detection methods of As,Cd and Pb in rice.Instrument conditions were determined As,Pb in 30 ? tube voltage,tube current 350 ?,test time 200 s;Cd in 70 ? tube voltage,tube current100 ?,inspection time 200 s has a good effect.The optimal detection conditions were determined when the sample was screened at 60 mesh and the sample volume of 3 g was kept at 15 MPa for 60 s.The standard curves of As,Pb and Cd were drawn,and the linear regression coefficients R2 of the curves were all greater than 0.99.The detection limits of the method were As: 0.08 mg/kg,Cd: 0.07 mg/kg,Pb: 0.06 mg/kg,which could meet the requirements of rapid detection of rice.The RSDS of 11 repeated tests of rice samples were 5.50%-7.18%,all of which were less than 10%,and the recoveries of spiked samples were 95.3%-109%.The co MParison between the present method and the standard method was made for 9 actual rice samples,and the relative errors of the two methods were in the range of-14.66%-8.85%.(3)Apply the quantitative method of basic parameters to establish the detection method of various elements in food and vegetables.The detection method of As,Pb,Cd,Cr,Ni,Cu,Zn,Rb and Mn in food,tablet and vegetable was established,and the detection conditions of elements were determined.The conditions of loading vegetable powder samples were optimized,and the optimal detection conditions were determined when the sample quantity of 2 g was kept at 15 MPa for 60 s.The LOD of multiple elements in vegetable samples was 0.07 ～0.32 mg/kg,RSDS of vegetable samples were3.0%～10.0%,recoveries were 80.0%～119%,and the detection precision and accuracy were good.(4)Verify the detection of Ad,Pb and Cd in rice by the food-tablet detection method based on the basic parameter method.The precision and accuracy of detection of As,Cd and Pb in rice by food-tablet were verified.The RSDS of 11 repeated tests were3.3%-9.2%,all of which were less than 10%,and the recoveries of spiked after calibration were 97.8%-110%.Nine actual rice samples were co MPared with the standard methods,and the relative errors of the two methods were in the range of-6.2%-9%,showing good detection precision and accuracy. |
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